The objective of this project is to survey organisms found in the environment, on plants, in the air, in food and water, in products used in care of cancer patients, and on personnel who work with them for the presence of potentially pathogenic micro-organisms. Means are sought to get rid of such organisms. Food items and products containing contamination are eliminated. More extensive studies of food are underway to determine if it serves as a major source of hospital acquired microorganisms. Various protective environments are also under evaluation for their use in protecting patients from acquisition of bacteria from the hospital. The study is designed to compare the effectiveness of protective environments afforded by laminar air-flow rooms, a new, more flexible "Med-Assist" air filtration system in combination with reverse isolation procedures and reverse isolation with no air filtration.